Liquid personal cleansing products are becoming more popular in the United States and around the world. Desirable liquid personal cleansing compositions must meet a number of criteria. For example, in order to be acceptable to consumers, a liquid personal cleansing product must exhibit good cleaning properties, must exhibit good lathering characteristics, must be mild to the skin (not cause drying) and preferably should even provide a moisturization benefit to the skin.
Liquid personal cleansing products which contain high levels of lipophilic skin moisturizing agents have been disclosed. In fact, consumer products, such as Oil of Olay Moisturizing Body Wash which, especially when used with the Olay Cleansing Puff, deposit lipophilic skin moisturizing agents on the skin are enormously popular with consumers. Nevertheless, some consumers would prefer to have an even greater moisturizing benefit delivered from these liquid personal cleansing products. Therefore, it would be desirable to provide a liquid personal cleansing composition with even greater moisturizing properties.
Oil of Olay Moisturizing Body Wash contains soybean oil as the lipophilic skin moisturizing agent. It has been found that superior deposition can be provided by other, more efficient, lipophilic skin moisturizing agents (e.g., petrolatum). Unfortunately, petrolatum, which contains a broad mixture of hydrocarbons, is incompatible with soluble surfactants in the isotropic micellular phase, the predominant surfactant structure employed in the liquid cleanser industry. The incompatibility stems from the solubilization of the low molecular weight hydrocarbon components of the petrolatum into the inner core of the elongated worm-like micelles where they transform the micelles from elongated aggregates to globular aggregates. This is analogous to the formation of microemulsion droplets. The net result of this transformation is rheology deterioration from the loss of elongated micelles and severe lather deterioration from the exponentially increased oil surface area (the result of surfactant binding). It has been found that oils which contain as little as 1% soluble components (e.g., petrolatum) are incompatible with soluble surfactants in the isotropic micellular phase.
In the past, the only solution to this problem was to utilize materials which, by themselves, are insoluble crystalline surfactant structures (e.g., soap) when employing nonpolar, soluble oils. See, for example, WO 94/01084 which discloses semisolid soap compositions comprising potassium C8-C22 free fatty acid soap, water, a polyol, petrolatum and C8-C22 free fatty acid and WO 96/02229 which discloses compositions comprising 5-35% C8-C22 fatty acid soap, petrolatum, and a structurant (e.g., fatty alcohols). This solution was not ideal since the insoluble crystalline surfactant imparted an unpreferred paste-like rheology in the presence of the soluble oils. Additionally, personal cleansing compositions incorporating the combination of insoluble crystalline surfactants and soluble oils tended to have stability problems and imparted an unpreferred draggy skin feel.
It has now been found, however, that liquid personal cleansing compositions which contain soluble oils or oils having soluble components, such as petrolatum, and soluble, non-crystalline synthetic surfactants and which exhibit good rheology, stability, skin feel and lathering characteristics can be obtained by manipulating the surfactant structure from the predominant and widely used micellular phase toward lamellar liquid structure, also known as the neat phase.